In this work, we investigate the decays of the fully open-flavor tetraquark state <math><msub><mi>X</mi><mn>0</mn></msub><mo>(</mo><mn>2900</mn><mo>)</mo></math> which was observed by the LHCb collaboration very recently. By using an effective Lagrangian approach, the partial widths of <math><msub><mi>X</mi><mn>0</mn></msub><mo>(</mo><mn>2900</mn><mo>)</mo></math> are estimated, where <math><msub><mi>X</mi><mn>0</mn></msub><mo>(</mo><mn>2900</mn><mo>)</mo></math> is assumed to be an <math><mi>S</mi></math>-wave <math><msup><mover><mi>D</mi><mo>¯</mo></mover><mo>*</mo></msup><msup><mi>K</mi><mo>*</mo></msup></math> hadronic molecule with <math><mi>I</mi><mo>=</mo><mn>0</mn></math>. It is found that the estimated results are in agreement with the experimental observations. Moreover, we also predict the decay behaviors of the other unobserved <math><msub><mover><mi>X</mi><mo>˜</mo></mover><mrow><mi>J</mi><mo>(</mo><mi>J</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>)</mo></mrow></msub></math>, which are the spin partners of the <math><msub><mi>X</mi><mn>0</mn></msub><mo>(</mo><mn>2900</mn><mo>)</mo></math> in the <math><mi>S</mi></math>-wave <math><msup><mover><mi>D</mi><mo>¯</mo></mover><mo>*</mo></msup><msup><mi>K</mi><mo>*</mo></msup></math> picture. It is pointed out that the <math><msub><mover><mi>X</mi><mo>˜</mo></mover><mn>1</mn></msub></math> state with <math><mi>I</mi><mo>=</mo><mn>0</mn></math> is a broad state with the width more than 100 MeV, while another <math><msub><mover><mi>X</mi><mo>˜</mo></mover><mn>2</mn></msub></math> state with <math><mi>I</mi><mo>=</mo><mn>0</mn></math> is a narrow state with the width approaching half of that for the <math><msub><mi>X</mi><mn>0</mn></msub><mo>(</mo><mn>2900</mn><mo>)</mo></math>. In addition, our results also show that the <math><msup><mover><mi>D</mi><mo>¯</mo></mover><mo>*</mo></msup><mi>K</mi></math> mode is expected to be the dominant decay mode for both <math><msub><mover><mi>X</mi><mo>˜</mo></mover><mn>1</mn></msub></math> and <math><msub><mover><mi>X</mi><mo>˜</mo></mover><mn>2</mn></msub></math>. Searching for those unobserved <math><msub><mover><mi>X</mi><mo>˜</mo></mover><mrow><mi>J</mi><mo>(</mo><mi>J</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>)</mo></mrow></msub></math> in the future experiments might be helpful to understand the nature of <math><msub><mi>X</mi><mn>0</mn></msub><mo>(</mo><mn>2900</mn><mo>)</mo></math>.

China

Cheng-Jian Xiao

Dian-Yong Chen

Yu-Bing Dong

Guang-Wei Meng

Study of the decays of <math><mi>S</mi></math>-wave <math><msup><mover><mi>D</mi><mo>¯</mo></mover><mo>*</mo></msup><msup><mi>K</mi><mo>*</mo></msup></math> hadronic molecules: The scalar <math><msub><mi>X</mi><mn>0</mn></msub><mo>(</mo><mn>2900</mn><mo>)</mo></math> and its spin partners <math><mrow><msub><mrow><mover><mrow><mi>X</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mi>J</mi><mo>(</mo><mi>J</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>)</mo></mrow></msub></mrow></math>

It is believed that there are more fundamental gauge symmetries beyond those described by the Standard Model of particle physics. The scales of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose considering the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of 
					 in the space-based interferometer detectors. Our study demonstrates that the GW energy spectrum is reachable by the LISA, Tianqin, Taiji, BBO, and DECIGO experiments only for the case where the spontaneous breaking of 
					 is triggered by at least two electroweak singlet scalars.
				

Wei Chao

Wen-Feng Cui

Huai-Ke Guo

Jing Shu

Gravitational wave imprint of new symmetry breaking JS is Supported by the National Natural Science Foundation of China (11647601, 11690022, 11675243) and also Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB23030100). Wei Chao is Supported by the National Natural Science Foundation of China (11775025)